Sequence Stratigraphy Research And Prediction Of Favorable Zones Of Shahejie Formation In Qikou Depression, Bohai Bay Basin

Qikou depression locates in Bohai bay basin, it is a classical continental rift basin developed on the basement of Mesozoic strata. Qikou depression is one of the largest and deepest sedimentary depressions in Bohai Bay basin, this paper takes shahejie formation as the research object.Based on the theories of EXXON sequence stratigrahy, sedimentology and petroleum geology etc, by integration of all available information and data of seismic, well logging, core and palaeontology, the high resolution sequence stratigraphy framework is built. The shahejie formation of qikou depression can be divided into five 3^rd-order sequences, and within the 3^rd-order sequence, by identifying of the FFS,MFS and major flooding surface, system tracts as well as 4^th -5^th sequence can be recognized, divided and correlated.Within the isochronic stratigraphy framework, by the study and analysis of lithofacies, seismic facies and electrofacies, depositional systems and facies including fluvial fan-fan delta, braided delta, basin floor fan, lacustrine are identified and recognized. In addition, the evolution and distribution of depositional systems and facies in the periods when shahejie formation was deposited are revealed. The control and influence of synsedimentary faults to sequence, system tracts, sand distribution system as well as depositional system and facies are discussed. Also, sequence stratigraphy models within different synsedimentary faults background are set up.Based on the research and analysis of fundamental reservoir forming factors, and in connection with the control and influence of synsedimentary fault to sand distribution system and facies, four favorable zones as reservoir exploration targets are predicted within the isochronic stratigraphy framework.